The invention concerns a vehicle wheel and, in particular, a wheel having special sound-absorbing properties.
When a vehicle travels over a road, its driver and passengers are seated in the passenger space in a very noisy environment. It is a constant concern of automobile manufacturers to limit the sound level of their vehicles as much as possible.
The sources of noise in the passenger compartment are highly varied. They include noises due to the engine, or of aerodynamic origin, or linked to the various hydraulic pumps or running noises of tires on the road.
The latter originate from the shocks sustained on running by the tire tread and which are audible in the passenger space of the vehicle. Such tire-running noises come within a very wide frequency range of between 80 and 800 Hz, notably with peaks toward 250 Hz. These noises are called xe2x80x9cbody humxe2x80x9d or xe2x80x9crunning noise.xe2x80x9d
In this frequency range, one encounters, in particular, a natural mode of vibration of the air toroid in the inner chamber of the tire, as well as four natural modes of vibration of standard wheels.
A great deal of research has been conducted to try to limit the noise in the passenger space of vehicles. For example, patent application JP 4-87803 proposes introducing a wall in the inner chamber of the tire in order to divide the inner air toroid into two parts, thereby substantially modifying its modes of vibration by displacing them beyond 500 Hz and, thus, attenuating the body hum noise peaks in the passenger space situated at approximately 250 Hz.
Another mode of action is described in application JP 6-106903. That application proposes introducing a sound-absorbing element, such as a foam, into the inner chamber of the tire, in order to attenuate the vibrations due to the resonance of the air toroid.
Application WO 98/02329 proposes a vehicle wheel in which the curved protuberance of the wheel disk is mechanically reinforced in order to raise the frequencies of several of the natural modes of vibration of the wheel. That application discloses that such a wheel makes it possible to attenuate the tire running noises heard in the passenger space of a vehicle.
The foregoing applications have not yet been put to any industrial use to date; consequently, the problem of effectively attenuating the noise heard in the passenger space of a vehicle is still pressing.
In the description that follows, the term xe2x80x9cprofilexe2x80x9d of a wheel is understood to be the geometry of a section of a wheel in any axial plane of the wheel.
In defining the xe2x80x9cinnerxe2x80x9d and xe2x80x9couterxe2x80x9d axial orientations relative to the median plane of a wheel, the xe2x80x9ccurved protuberancexe2x80x9d is understood to be the axially outermost part of the disk between the zone of attachment to the vehicle and the zone of connection with the rim (see FIG. 1).
When a wheel presents, in side view and from the outside, a visual continuity between the disk and the outer tire-mounting hook or flange, such a wheel is called a xe2x80x9cfull-facexe2x80x9d wheel. Such visual continuity can be obtained by incorporating the outer flange in the disk and by assembling the disk and the rim at the outer end of the outer tire-bead seat. Such a wheel is disclosed in U.S. Pat. No. 5,509,726. A disk containing an intermediate zone can also be obtained between a zone of connection of the disk to the rim and a zone of attachment of the disk to the vehicle, which disk extends in the radial direction generally to the outer end of the outer seat of the rim.
The present invention concerns a vehicle wheel comprising a rim and a disk, the disk presenting a generally annular center zone of attachment of the disk to the vehicle and a zone of connection of the disk and the rim, as well as a radially intermediate zone. In accordance with the invention, the intermediate zone of the disk contains an angular sector, or two given diametrically opposite angular sectors, which is, or are, stiffened against axial bending relative to any other angular sector of the same central angle.
Consequently, the tilting rigidity of the wheel relative to an axis passing through the zone of attachment of the disk to the vehicle is maximal when the axis is at right angles to the center axis of the given angular sector or sectors.
As will be explained below, the wheel according to the invention provides a frequency split of one of the natural modes of vibration of the disk. The mean vibration frequency of the two resulting natural modes of vibration is greater than the frequency of the same natural mode of a comparable standard wheel.
The applicants have observed that such a wheel possesses remarkable properties of attenuation of the body hum noise detected in the passenger space of a vehicle equipped with such wheels.
By way of example, a wheel according to the invention includes, in the given angular sector or sectors and in at least one part of the disk profile, an increase in at least one geometric parameter chosen from the group consisting of the disk thickness, the axial distance relative to the median plane of the wheel, and the radial distance relative to the axis of rotation of the wheel.
When the intermediate zone of the wheel disk includes a zone of openings and a curved protuberance, the thickness, the axial position and/or the radial position of the curved protuberance in the given angular sector or sectors can be increased. Such increases can be continuous or discontinuous. In the latter case, localized bosses can be provided, for example.
The intermediate zone of a wheel according to the invention can be locally stiffened by ribs of radial orientations, for example, by welded reinforcements or by a localized reduction of surface area of its openings.
The zone of openings can also be stiffened locally by means of openings containing means of stiffening, such as beads.
According to another embodiment, in the one or two given angular sectors, the link between the disk and the rim is arranged under the outer seat of the rim. In the other sectors, the link is arranged under the rim well.
According to an alternative embodiment, in the one or two given angular sectors, the link between the disk and the rim is arranged under the outer hook or flange of the rim. In the other sectors, the link is arranged under the rim well.